1. Field of the Invention
The present invention relates to a generator system utilizing a fuel cell and more particularly to a generator system utilizing a fuel cell of the type in which the output of the fuel cell is controlled in response to an amount of energy charged in a battery.
2. Description of the Prior Art
In general, a fuel cell cannot supply fuel to the fuel cell in response to variation in a load so that when the load to which the power is supplied from a generator system utilizing a fuel cell is a variable load, it has been considered that the fuel cell is backed up by a battery.
More particularly, when the load current is greater than the output current derived from the fuel cell, the battery delivers the additional power to the load. On the other hand, when the load current is smaller than the output current derived from the fuel cell, an excess of the power to be supplied to the load is charged into the battery.
However, when a light load continues or when the battery is charged with the output current derived from the fuel cell, there is a fear that the battery might be overcharged so that the charging condition must be monitored, thereby controlling the charging current. In case the charging current is not controlled, there arises the problem that the battery is damaged or its performance is degraded.
Furthermore, in the fuel cells, the consumption of fuel is decreased, an excessive gas is produced. In the case of a fuel cell of the type which uses a gas reformed in a reformer, a part of the reformed gas supplied to the fuel-cell electrode which does not occur a chemical reaction becomes an off-gas and burns the burner of the reformer. Therefore, because of the excessive gas supplied to the burner, the reformer is overheated so that the qualities of the reforming catalysts are degraded or the reformer itself is damaged.
In the case of the hybrid system comprising a commercially available power source and a battery, a CVCF (constant-voltage constant-frequency) control devices have been proposed and used in practice, but they are still objects to be studied including the above-described problems in the hybrid system comprising a fuel cell and a battery.